MP2303A Datasheet, PDF (8/15 Pages) Monolithic Power Systems – 3A, 28V, 360kHz Synchronous Rectified Step-Down Converter

MP2303A – 3A, 28V, 360kHz SYNCHRONOUS RECTIFIED, STEP-DOWN CONVERTER
BLOCK DIAGRAM
+
0.95V --
FB
+
0.3V --
OVP
RAMP
OSCILLATOR
360kHz
CLK
--
SS
+
0.8V +
ERROR
AMPLIFIER
CURRENT
SENSE
AMPLIFIER ₊
--
+
SQ
RQ
--
CURRENT
COMPARATOR
IN
5V
BS
SW
COMP
EN
1.2V
--
1.3 V +
SHUTDOWN
COMPARATOR
Figure 1—Functional Block Diagram
OVP
IN < 3.95V
GND
IN
INTERNAL
REGULATORS
OPERATION
FUNCTIONAL DESCRIPTION
The MP2303A is a synchronous rectified,
current-mode, step-down regulator. It regulates
input voltages from 4.7V to 28V down to an
output voltage as low as 0.80V, and supplies up
to 3A of load current.
The MP2303A uses current-mode control to
regulate the output voltage. The output voltage
is measured at FB through a resistive voltage
divider and amplified through the internal
transconductance error amplifier. The voltage at
COMP pin is compared to the switch current
measured internally to control the output
voltage.
The converter uses internal N-Channel
MOSFET switches to step-down the input
voltage to the regulated output voltage. Since
the high side MOSFET requires a gate voltage
greater than the input voltage, a boost capacitor
connected between SW and BS is needed to
drive the high side gate. The boost capacitor is
charged from the internal 5V rail when SW is low.
When the MP2303A FB pin exceeds 20% of the
nominal regulation voltage of 0.80V, the over
voltage comparator is tripped and latched; the
COMP pin and the SS pin are discharged to
GND, forcing the high-side switch off.
MP2303A Rev.1.1
www.MonolithicPower.com
8
7/25/2012
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